Dog platelets accumulate intracellular Fibrinogen as they age
Article first published online: 4 FEB 2005
Copyright © 1994 Wiley-Liss, Inc.
Journal of Cellular Physiology
Volume 161, Issue 1, pages 23–30, October 1994
How to Cite
Heilmann, E., Hynes, L. A., Friese, P., George, J. N., Burstein, S. A. and Dale, G. L. (1994), Dog platelets accumulate intracellular Fibrinogen as they age. J. Cell. Physiol., 161: 23–30. doi: 10.1002/jcp.1041610104
- Issue published online: 4 FEB 2005
- Article first published online: 4 FEB 2005
- Manuscript Accepted: 29 MAR 1994
- Manuscript Received: 1 DEC 1993
The alpha granules of circulating platelets are dynamic structures that acquire endogenous and exogenous components by synthesis and uptake, respectively. The uptake of exogenous components is a result of either receptor-mediated endocytosis or fluid-phase pinocytosis. Despite many detailed studies on the function and content of α-granules, little is known of the impact of platelet age on these organelles. In this report, we describe the use of platelet biotinylation to identify and isolate aged platelets for the analysis of α-granule contents. When aged platelets were permeabilized and examined by flow cytometry utilizing fluorescently labeled antibodies, two exogenously acquired proteins, fibrinogen and immunoglobulin G, were found to increase significantly with platelet age. The levels of intracellular fibrinogen were found to be elevated relative to control, 114 ± 2% and 119 ± 5% on days 4 and 5 postbiotinylation, respectively; the life span of dog platelets is 6.0 days. Intracellular immunoglobulin G content increased similarly. Levels of two endogenously synthesized proteins, thrombosponding and P-selectin, were not elevated in aged platelets. Confirmation of the flow cytometric data was obtained by isolating aged, biotinylated platelets by fluorescence-activated cell sorting and quantitating the fibrinogen levels with an ELISA assay. For platelets averaging 4.6 days of age, the fibrinogen level was elevated to 128 ± 23% of the level for the entire platelet population. These data demonstrate that age-dependent changes in exogenously acquired α-granule proteins do occur and that the uptake mechanism for these proteins is active through out the platelet life span. © 1994 Wiley-Liss, Inc.